feat(core): implement Git repository operations with gRPC services

- Add advertise_refs functionality for Git protocol communication
- Implement archive service with TAR/ZIP format support and streaming
- Create blame service for Git file annotation with line tracking
- Add branch management including create, delete, rename and compare operations
- Implement merge checking with conflict detection and fast-forward handling
- Add cherry-pick functionality for applying commits between branches
- Integrate gix library for Git repository operations and object handling
- Add comprehensive test suite covering all Git operations
- Implement proper error handling and repository validation
- Add pagination support for large result sets
- Create protobuf definitions for all Git operations and data structures
- Add build system for gRPC code generation and dependency management

proto/archive.proto

@@ -0,0 +1,58 @@
+syntax = "proto3";
+
+package gitks;
+
+import "oid.proto";
+import "repository.proto";
+
+message ArchiveOptions {
+  enum Format {
+    ARCHIVE_FORMAT_UNSPECIFIED = 0;
+    ARCHIVE_FORMAT_TAR = 1;
+    ARCHIVE_FORMAT_TAR_GZ = 2;
+    ARCHIVE_FORMAT_TAR_BZ2 = 3;
+    ARCHIVE_FORMAT_TAR_XZ = 4;
+    ARCHIVE_FORMAT_ZIP = 5;
+  }
+
+  Format format = 1;
+  string prefix = 2;
+  repeated string pathspec = 3;
+  int32 compression_level = 4;
+  bool include_global_extended_pax_headers = 5;
+}
+
+message ArchiveRequest {
+  RepositoryHeader repository = 1;
+  ObjectSelector treeish = 2;
+  ArchiveOptions options = 3;
+}
+
+message ArchiveChunk {
+  bytes data = 1;
+}
+
+message ArchiveEntry {
+  string path = 1;
+  Oid oid = 2;
+  uint32 mode = 3;
+  int64 size = 4;
+  ObjectType type = 5;
+}
+
+message ListArchiveEntriesRequest {
+  RepositoryHeader repository = 1;
+  ObjectSelector treeish = 2;
+  repeated string pathspec = 3;
+  Pagination pagination = 4;
+}
+
+message ListArchiveEntriesResponse {
+  repeated ArchiveEntry entries = 1;
+  PageInfo page_info = 2;
+}
+
+service ArchiveService {
+  rpc GetArchive(ArchiveRequest) returns (stream ArchiveChunk);
+  rpc ListArchiveEntries(ListArchiveEntriesRequest) returns (ListArchiveEntriesResponse);
+}